The present invention relates to golf balls, and particularly to a golf ball which has dimples which are evenly and uniformly distributed so that the ball has fifteen axes of symmetry. Each axis of symmetry is not an actual parting line drawn on the surface of the golf ball, but a false parting line for uniformly arranging dimples over the surface of the golf ball.
Such false parting lines are utilized for distributing dimples of various sizes uniformly and symmetrically over the surface of the golf ball without leaving dimple-free areas, thus eliminating either heavy concentrations of dimples or rarefied areas in which the dimple spacing is large, minimizing multiple parallel straight rows of dimples formed by the said false parting lines, and distributing dimples of various sizes uniformly and symmetrically over the surface of the golf ball. Accordingly, an ideal golf ball should have a plurality of axes of symmetry, but no parallel straight rows of dimples and in case multiple dimple sizes are used, the various sized dimples should be distributed and mixed uniformly and symmetrically over the surface of the ball.
In order to improve consistency and accuracy of golf ball dimples, various attempts have been made to distribute dimples over the surface of golf ball with many axes of symmetry and without dimple-free areas and to eliminate parallel straight rows of dimples.
For example, Korean Patent Publication No. 80-1003 describes a golf ball in which spherical surface of the ball is divided into twelve regular pentagons A, as shown in FIG. 1, each pentagon A subdivided by ten parallel parting lines into outer quadrangulars 1, inner triangles 2 and an inner regular pentagon 3. 360 dimples are distributed over the surface of the ball by providing four dimples for each outer quadrangular 1, one dimple for each inner triangle 2 and five dimples for one inner regular pentagon 3. However, the golf ball has only ten axes of symmetry.
If the above case and the present invention are applied to same sized golf balls and if one of twelve pentagons A corresponding to the faces of a regular dodecahedron is assumed as a unit, this unit should have the theoretical area which is 1.2 times as large as that of the unit of the present invention. Accordingly, the number of the axes of symmetry, twelve, is calculated by 1.2 times 10(axes of symmetry).
FIG. 2 shows a case in which the surface of golf ball is divided into twenty regular triangles B, each of which is subdivided into six right-angled triangles 4. 360 dimples are distributed over the surface of the ball by providing three dimples for each right-angled triangles 4. In this invention, too, the golf ball has no more than ten axes of symmetry.
If the above case and the present invention are applied to same sized golf balls and if one of twenty regular triangles B corresponding to the faces of a regular icosahedron is assumed as a unit, this unit should have the theoretical area which is twice as large as that of the unit of the present invention. Accordingly, the number of the axes of symmetry is calculated at ten.
U.S. Pat. No. 4,560,168 describes a golf ball in which the surface of the ball is divided into twenty regular triangles C, as shown in FIG. 3. Each triangle is further divided into four regular triangles, that is, three apical triangles 5 and one central triangle 6. Dimples are arranged in each apical triangle 5 and each central triangle 6, so that no dimples intersect the sides of the central triangle 6. However, the golf ball of this case has only nine axes of symmetry.
If the above case and the present invention are applied to same sized golf balls and if one of twenty regular triangles C corresponding to the faces of a regular icosahedron is assumed as a unit, this unit should have the theoretical area which is twice as large as that of the unit of the present invention. Accordingly, the number of the axes of symmetry is calculated at nine.
However, the above-mentioned conventional dimple patterns have a disadvantage of having multiple parallel straight rows of dimples which are formed when dimples are arranged on multiple pararrel straight lines formed by each triangle unit B or C, as indicated by two-dotted lines in FIGS. 2 and 3.